The present invention relates generally to a manner by which to maintain communication quality levels at a desired level in a radio communication system when communications with a mobile station are handed-off from a serving cell to a target cell. More particularly, the present invention relates to apparatus, and an associated method, by which to select a cell likely to become a target cell based upon movement of the mobile station within the serving cell, prior to a request for a hand-off of communications to a target cell. Once the likely target cell is selected, resources at the likely target cell are reserved, thereby to ensure better that the resources are available, subsequent the handover, to maintain communications at the desired communication quality level.
Communication signals communicated between a sending station and a receiving station of a communication system provide for the communication of information between the sending station and the receiving station. The sending station and the receiving station are interconnected by way of a communication channel upon which the communication signal is communicated. The communication signals formed by the sending station are of characteristics to permit their transmission upon the communication channel. And, when the communication signal is received at the receiving station, the receiving station recreates the informational content contained in the communication signal.
When the communication channel is formed of a radio channel defined upon a portion of the electromagnetic spectrum, the communication system is referred to as a radio communication system. A wireline connection is not required to interconnect the sending station and a receiving station in a radio communication system; therefore, communications are possible in a radio communication system even when a wireline connection formed between the sending and receiving stations would be impractical.
A cellular communication system is an exemplary type of radio communication system. Various cellular communication standards have been promulgated, and cellular communication systems have been implemented pursuant to such promulgated standards. And, additional cellular communication systems continue to be proposed and improvements to existing cellular communication systems have similarly also been proposed.
Generally, a cellular communication system typically includes a network infrastructure including fixed-site, base transceiver stations positioned at spaced intervals throughout a geographic area. Each of the base stations defines a coverage area, referred to as a cell, within which radio communications with a mobile station are possible. The mobile station typically is movable such that the mobile station might initially be positioned in a first cell, referred to as a serving cell, and thereafter be repositioned in another cell, referred to as a target cell. Handover of communication with the mobile station from the base station encompassing the serving cell to the base station encompassing the target cell permits continued communications with the mobile station.
For a handover of communications from the serving cell to the target cell to be effectuated, however, resources must be available at the target cell. Resources refer, amongst other things, to radio channel allocations to permit the effectuation of a communication service with the mobile station. If the radio channels are being used to effectuate communications with other mobile stations, radio channel capacity might not be available to permit communications to be handed off from the serving cell to the target cell with the mobile station entering the target cell. In such an occurrence, handover of communications to the target cell might not be permitted. Or, if handover is permitted, the communication service might be required to be performed at a degraded quality of service level. If an attempt is made to effectuate the communication service at a degraded quality of service level, a noticeable diminution of quality of the communication service might occur.
By earlier requesting reservation of the resources at the target cell, the likelihood that the resources shall become available at the target cell by the time when handover is to occur is increased. Thereby, one manner by which better to ensure that resources shall be available at a target cell to permit continuation of a communication service at a desired quality of service level would be to reserve such resources at every cell which could possibly form the target cell. However, reserving resources at every possible target cell would be an impractical solution in many situations. Reserving resources at cells likely to form target cells would, in contrast, increase the likelihood that the resources would be available at the target cell when a handover is to occur without unduly reserving resources at the cells which do not become the target cell.
If a manner could be provided, therefore, to determine which cell, or cells, are likely to be the target cell, or cells, improved communication in the cellular, or other radio, communication system would be possible. Responsive to a determination of the likely target cell, or cells, a request could be made to reserve the resources at the likely target cell, or cells, better to ensure that the resources shall be available at the cell when a handover of communications is to be effectuated.
It is in light of this background information related to communications in a cellular, or other radio, communication system that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides apparatus, and an associated method, to facilitate maintenance of communication quality levels at a desired level in a radio communication system when communications with a mobile station are handed-off from a serving cell to a target cell.
Selection is made of one or more cells likely to become a target cell based upon movement of the mobile station within the serving cell, prior to a request for hand-off of communications to the target cell. By selecting a likely target cell prior to a request for the hand-off of the communications to the target cell, resources at the likely target cell can be reserved, thereby to ensure that the resources shall be available to continue the effectuation of the communication service with the mobile station without degradation of quality levels of the communication service.
In one aspect of the present invention, the mobile station is provided with apparatus to permit determination, at the mobile station, of the positioning of the mobile station. In one implementation, the mobile station includes a GPS (Global Positioning System) receiver operable to receive conventional, global positioning signals generated by GPS satellites. The GPS receiver forming a portion of the mobile station is operable to determine longitudinal and latitudinal positioning of the mobile station responsive to the reception of the GPS signals. By recalculating the positioning of the mobile station in this matter at two or more times, the velocity of the mobile station is further determinable. That is to say, by determining the positioning of the mobile station at separate locations at a known time interval, the speed and heading of the mobile station is readily calculable. Responsive to such measurements and calculations, an estimate can be made both of which cell, or cells, shall likely be a target cell to which handover of communications shall subsequently need to be effectuated and also of when the handover shall likely be necessary. Through such information, a request to reserve resources at a likely target cell can be made and resources can subsequently be allocated thereto so that continued communications at a desired service quality level subsequent to handover of communications is better assured.
In another aspect of the present invention, apparatus is provided for the network infrastructure of the cellular communication system to select one or more cells to be a likely target cell, or cells, to which communications are to be handed-over as a mobile station travels out of a serving cell and into a target cell. The resource reserver receives indications of the positioning of the mobile station and the velocity at which the mobile station is traveling. The resource reserver is also coupled to receive indications of the communication quality level of which a communication service effectuated with the mobile station is being performed. The resource reserver, responsive to the indications of the positioning and velocity of the mobile station, selects a likely target cell, or cells, into which the mobile station shall subsequently travel. Also, responsive to the indications of the positioning and of the velocity of the mobile station, the resource reserver estimates when the mobile station shall likely enter the likely target cell. With further use of the information related to the service quality level at which the communication service is presently being effectuated, or otherwise desired, pursuant to a service subscription of the mobile station to operate in the communication system, the amount, and type, of resources needed to be reserved at the likely target cell is also determinable. Such resources can thereby be requested to permit continuation of effectuation of the communication service at the service quality level subsequent to handover of communications from the serving cell. By early-requesting the resources to be allocated to the mobile station in the likely target cell, the resources are more likely to be allocated to the mobile station, and available for use therewith when a request for handover of communications occurs. As a result, maintenance of the service quality level at which the communication service is desired to be effectuated shall more likely be possible.
In one implementation, an embodiment of the present invention is implementable in an IS-2000, cellular communication system. Such a cellular communication system is to provide for communication services necessitating different levels of communication resources, such as channel bandwidth, for their effectuation. Also, the system sets forth QoS (Quality of Service) levels at which a communication service can, or must, be effectuated. A subscriber to the communication system, for instance, subscribes, pursuant to a service subscription, for a selected level of service. Through operation of an embodiment of the present invention, better assurances are provided that the desired QoS level at which a communication service is effectuated can be maintained when handover of communications with a mobile station occurs. Determinations are made at the mobile station as to the positioning of the mobile station as well as the speed and heading, i.e., the velocity, of the mobile station. Indications of the values of the positioning of the mobile station as well as the velocity thereof are sent, by way of a radio link, to the network infrastructure of the system. The information is sent to the network infrastructure together with a pilot strength measurement (PSMM) signal. A resource reserver located at the base station which forms the serving base station uses the information sent thereto to select a likely target cell to which the mobile station shall likely enter, as well as the time at which the mobile station shall likely enter the target cell. The serving base station also has knowledge of the resource requirements to effectuate the communication service with the mobile station at a selected service quality level. From such information, the resource reserver at the serving base station is able to request from corresponding structure at a target base station to reserve resources thereat, thereby to assure that resources shall be available to be allocated to the mobile station upon subsequent handover of communications to the target cell.
In these and other aspects, therefore, apparatus, and an associated method, is provided for selecting a target coverage area defined by at least one target, fixed-site transceiver forming a portion of a radio communication system. The radio communication system includes a plurality of spaced-apart, fixed-site transceivers positioned throughout a geographic area. Each fixed-site transceiver defines a coverage area within which communications with a mobile station are permitted pursuant to a service subscription. The target coverage area is selected at which to reserve resources to communicate with the mobile station at a selected quality of service level subsequent to handover of communications by a serving, fixed-site transceiver. A resource reserver is coupled to receive an indication of positioning of the mobile station and an indication of a velocity at which the mobile station is traveling. The resource reserver is operable responsive thereto to select the at least one target, fixed-site transceiver at which to reserve the resources and to select when to reserve the resources.